The variants iResolution, iMouse and iGlobalTime can also be used for
legacy reasons.

Textures

Textures can be loaded by defining a uniform with a comment containing the path
to the file. The syntax is:

uniform sampler2D <texture_name>; // <path_to_file>

For example:

uniform sampler2D inThisDirectory; // foo.jpg

uniform sampler2D inOtherDirectory; // ../other_textures/bar.png

uniform sampler2D withAbsolutePath; // /Users/ford/textures/blah.bmp

Shader errors

If the shader fails to compile, the tab and line number will subtly highlight in
red.

If enabled in the package settings, a notification will show the error message:

Capture images

Right click on the preview to copy or save a still image of the shader. This can
also be done by running the command "Glsl Preview: Copy Image" or
"Glsl Preview: Save Image" from the command palette (cmd-shift-P).